immunology

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Immunology
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IMMUNOLOGY AND THE IMMUNE SYSTEM

• Immunology
• Study of the components and function of the
  immune system
• Immune System
• Molecules, cells, tissues and organs which
  provide non-specific and specific protection
  against
• Microorganisms
• Microbial toxins
• Tumor cells
• Immune system is crucial to human survival

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Levels of defense against pathogens
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First line of defence non-specific barriers

• These are a combination of physical and chemical
  barriers that prevent all types of foreign agents
  from penetrating the outer layer of the body. No
  specific foreign agent is targeted at this level.
• The barriers are
• The skin  excellent barrier to pathogens.
• Mucous membranes  line the entrances to the body
  such as in the respiratory tract entrances. Mucus
  produced by these membranes traps foreign
  particles and directs them out of the body.
• Hair  (nasal hair) trap dust and dirt.
• Gastric juice, vaginal secretions and urine 
  acidic fluids that have a protective function.
• Tears, sweat and saliva  body fluids which
  possess some anti-bacterial properties.
• Cerumen (ear wax) produced in the ear canal and
  protects the canal by trapping dirt and dust
  particles.

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First line of defense Surface membrane barriers

• Skin and mucous membrane
• Layered epidermis and shedding of epithelial
  cells
• Sebum inhibits growth of bacteria and fungi
• Mucous traps microbes, dust and pollutants.
• Lacrimal apparatus
• Saliva
• Vaginal secretions
• Flow of urine
• Defecation and vomiting
• Gastric juices destroy bacteria and their toxins

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Other 1st Line Defenses
Oral Cavity Antimicrobial enzymes in saliva (e.g. lysozyme and lactoperoxidase) inhibit microbes, Resident flora
Skin pH (3-5), sebum
Respiratory Cavity Hairs, cilia, mucociliary escalator, Sticky mucus (lysozyme) traps dust and microbes.
GI Tract low pH and digestive enzymes, flushing action
Eyes Tears, (lysozyme). flushing action
Vagina pH, flushing action, resident flora
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Definitions

• Antigen (Ag)
• Foreign substance that, when introduced into the
  body, is capable of stimulating an immune
  response
• Antibody (Ab) / also called immunoglobulin (Ig)
• A protective protein produced by the immune
  system in response to the presence of a foreign
  substance, called an antigen
• There are 5 types of anibody (IgM, IgA, IgG, IgE,
  IgD)
• Antibiotics
• Antibiotics are powerful medicines that
  fight bacterial infections
• Overuse of antibiotics can weaken the efficiency
  of the immune system

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5 types of anibody (IgM, IgA, IgG, IgE, IgD)
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Immune response to infection involves

• 1- RECOGNITION locate and identify the pathogen
• 2- DEFENSE repel and destroy the pathogen

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THE IMMUNE RESPONSE AND IMMUNITY

• Immune response
• Innate (non-specific)
• Adaptive (specific)
• Immunity
• State of non-specific and specific protection
• Acquisition of Immunity
• Natural
• Examples
• 1- Antibodies in the breast milk of mothers.
• 2- Overcome an infection ex. Chicken pox
• Artificial
• Example vaccination

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DEFENSE MECHANISMS OF THE HUMAN HOST

• Innate Mechanisms (Innate immunity)
• Second line of defense
• Non-specific
• Adaptive Mechanisms (Adaptive immunity)
• Third line of defense
• Highly specific with memory
• Cooperation between mechanisms

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WHAT ARE STEM CELLS?

• Stem cells have the remarkable potential to
  develop into many different cell types in the
  body during early life and growth.

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Innate Immune Response at sites ofInfection
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Examples of Cells participate in innate immunity

• Phagocytes- consists from
• Macrophage (MF) As cells that function in
  virtually all body tissues, macrophages are
  highly flexible, which allows them to efficiently
  perform their functions and respond appropriately
• Neutrophil have long been viewed as the final
  effector cells of an acute inflammatory response,
  with a primary role in the clearance of
  extracellular pathogens.
• 2. Natural killer cell (NK Cell) large granular
  lymphocytes (LGL), are a type of cytotoxic
  lymphocyte critical to the innate immune system
  that belong to the rapidly expanding family of
  known innate lymphoid cells (ILC) and represent
  520 of all circulating lymphocytes in humans.
• 3. Mast cell are evolutionarily conserved,
  tissue-resident immune cells with diverse roles
  in allergy, cancer, and protection from infection
  by helminths and microorganisms

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Interferons

• Produced by lymphocytes, macrophages and
  fibroblasts.
• Interfere with translation of viral proteins
• Degrade viral RNA
• Activate macrophages and NK cells
• Interferon Animation

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Complement
Complement Cascade Animation
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Phagocytosis
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Phagocyte Mobilization
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Adaptive immunity

• Adaptive immunity refers to antigen-specific
  immune response. The adaptive immune response is
  more complex than the innate. The antigen first
  must be processed and recognized. Once an antigen
  has been recognized, the adaptive immune system
  creates an army of immune cells specifically
  designed to attack that antigen. Adaptive
  immunity also includes a "memory" that makes
  future responses against a specific antigen more
  efficient.  Antigen-presenting cell (APC) like
  Dendritic cells and some Macrophages play the
  role of  linking between the innate and adaptive
  immune systems

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Cells of the adaptive immune system

• Cells that make up the adaptive (specific) immune
  system include the B and T lymphocytes.
•   After exposure to antigen, B cells
  differentiate into plasma cells whose primary
  function is the production of antibodies. 
  Similarly, T cells can differentiate into either
  T cytotoxic (Tc) or T helper (Th) cells

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PRIMARY AND SECONDARY ANTIBODY RESPONSE

• Primary Response
• Following exposure to an antigen, there is a slow
  rise in IgM followed by a slow rise in IgG
• Secondary Response
• Following exposure to previously encountered
  antigen, there is a rapid rise in IgG and slow or
  no rise in IgM
• Memory or anamnestic response

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Innate immunity Adaptive immunity
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DISORDERS OF THE IMMUNE SYSTEM

• Hypersensitivity Reactions
• Over-reaction of adaptive immune response to
  harmless antigens
• Four Types of reactions (I,II,III and IV)
• Autoimmunity
• Misdirected adaptive immune response
• Results from a loss of self-tolerance
• Three Types (II, III, IV) of reactions
• Immunodeficiencies
• Components of immune system either absent or
  defective (example acquired immune deficiency
  syndrome AIDS)
• Genetic or acquired etiology